The Patient Electronic Monitoring Systems (PEMS), which locks the Unit doors and alerts the nursing staff when a patient tries to leave the Nursing Unit, is a welcome aid in the care of patients with Alzheimer's disease or other dementias. A detector unit, placed at each of two exit doors, senses the presence of any patient wearing a wristwatch-size radio transmitter. Upon detection of a patient's transmitter, an embedded computer-based controller locks the exit door, activates an alarm, and displays the patient's name and location on a PC monitor. The Clinical Center requested that an updated design of the PEMS be installed on the 5E and 3E Nursing Units, and that the obsolete controller on the 6D Nursing Unit be replaced with the newly designed version.